Effect of organic and mineral fertilization on proximate composition of three leafy vegetables harvested at different periods

Abstract

Leafy vegetables are part of natural resources traditionally harvested from forests in Benin. Some of these wild plants foods have been introduced in the small scale production system. The low productivity and the increasing demand for such products urged to use fertilizers. However, the impact of such practices on the nutritional properties of these leaves was poorly documented. In this study Sesamum radiatum, Ceratotheca sesamoïdes and Justicia tenella were cultivated using NPK, cowpat and mixture of NPK plus cowpat. Leaves harvested at 6, 9, 10, 12 or 14 weeks after transplanting were analyzed for proximate composition. Protein content ranged from 17.2 to 33.8 g/100 g DW; ash from 7.7 to 20.4 g/100 g; fat from 1.2 to 7.3 g/100 g, fiber from 5.6 to 13.1 g/100 g and polyphenols content from 0.24 to 1.33 g GAE/100 g (DW). Significant effects of species, fertilizer and cutting time were evidenced. Whereas ash content increased by 1 to 25.8% ratio in fertilized S. radiatum leaves, it showed a downward trend (-1 to -22%) during the two first cutting times of C. sesamoides followed by an upward trend (12.7 to 14.3%) at the last cutting time, in comparison to the non fertilized leaves.